Field of the Invention
The present invention relates generally to a turbo machine, and more specifically to a gas turbine engine with an air riding seal formed between a rotor and a stator of a turbine in which the air riding seal is self-balancing.
Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a gas turbine engine, such as a large frame heavy-duty industrial gas turbine (IGT) engine, a hot gas stream generated in a combustor is passed through a turbine to produce mechanical work. The turbine includes one or more rows or stages of stator vanes and rotor blades that react with the hot gas stream in a progressively decreasing temperature. The efficiency of the turbine—and therefore the engine—can be increased by passing a higher temperature gas stream into the turbine. However, the turbine inlet temperature is limited to the material properties of the turbine, especially the first stage vanes and blades, and an amount of cooling capability for these first stage airfoils.
A seal is required between a stator and a rotor of a turbine in order to prevent a main stream gas flow from leaking into a rim cavity where the rotor disk surfaces can be affected by high thermal loads. One effective seal is an air riding or seal disclosed in U.S. Pat. No. 8,066,473 issued to Aho, J R. on Nov. 29, 2011 and entitled FLOATING AIR SEAL FOR A TURBINE, the entire contents being incorporated herein by reference. The Aho, J R. air riding seal provides a very effective seal with a minimal of wear for the high temperature environment for which the seal is used.
One problem with the Aho, J R. air riding seal is during engine transients such as when the gas turbine engine is shut down or started up. During these transient phases, the pressure balance equilibrium across the seal is perturbed causing the potential for the seal to contact the rotor creating wear and premature failure. The present invention provides a means to ensure the seal doesn't contact the rotor under any circumstances as well as the ability to control the activation of the seal.